html, body {
	padding: 0;
	margin: 0;
	width: 100%;
	height: 100%;
}

.container {
	background-image: url(../img/bg.jpg);
	width: 100%;
	height: 100%;
	background-size: 100% 100%;
	background-repeat: no-repeat;
}

form {
	/* text-align是可以被子元素继承 */
	text-align: center;
	position: absolute;
	left: 50%;
	top: 50%;
	transform: translate(-50%, -50%);
}

form input {
	border: none;
	border-bottom: 2px solid black;
	background-color: transparent;
	color: white;
	outline: none;
	padding: 5px;
}

form input:focus {
	border-bottom-color: pink;
}

.btn {
	width: 120px;
	height: 40px;
	border: none;
	outline: none;
	background-size: 100% 100%;
	background-color: transparent;
}

.btn-login {
	background-image: url(../img/btn_login_p.png);
}

.btn-login:hover {
	background-image: url(../img/btn_login_n.png);
}

.btn-logout {
	background-image: url(../img/btn_logout_p.png);
}

.btn-logout:hover {
	background-image: url(../img/btn_logout_n.png);
}

::-webkit-input-placeholder { /* WebKit browsers */
  color: #fff;
}

::-moz-placeholder { /* Mozilla Firefox 19+ */
  color: #fff;
}

:-ms-input-placeholder { /* Internet Explorer 10+ */
  color: #fff;
}